The invention relates to a patient monitor used to monitor gas concentrations. In particular, the patient monitor includes a module that facilitates a conversion from mainstream gas concentration measurement to sidestream gas concentration measurement.
Patient monitors are used to monitor and display patient data, typically in a medical setting. Examples of measured parameters may include electrocardiogram data, non-invasive blood pressure, impedance respiration, SpO2, and temperature. Further, patient monitors may be used to monitor the carbon dioxide (CO2) in a patient""s breath during a respiratory cycle. Such measurement of carbon dioxide concentration over time is referred to as capnography and is used to assess the adequacy of patient ventilation, patient cardiac function, and other related patient functions.
In general, capnography data is presented on a patient monitor via a wave form or numerical data that displays the carbon dioxide level in the patient""s breath, measured in kPa, mmHg, percent, or equivalent dimension. One capnography parameter that is particularly useful is the amount of carbon dioxide at the end of each breath, known as end-tidal carbon dioxide (EtCO2). EtCO2 may be used to calculate an approximate value of carbon dioxide pressure in arterial blood, which provides information as to the patient""s cardiovascular and respiratory system functionality.
There are several different ways that the concentration of exhaled carbon dioxide may be measured. Methodologies may include photoacoustic spectroscopy, mass spectrometry, Raman scattering measurement, and infrared absorption spectroscopy (IR spectroscopy). IR spectroscopy is a common method utilizing a light source to transmit a beam of light through a gaseous sample. The light beam has a wavelength that is preferentially absorbed by CO2. The transmitted radiation is measured by a photodetector. The amount of absorbed radiation indicates the concentration of CO2 in the sample volume. A commonly used wavelength for IR spectroscopy when used to measure carbon dioxide concentration is 4.3 microns.
Two types of gas analyzers may be used to measure gas concentrations, such as carbon dioxide. Mainstream gas analyzers are typically located at a patient""s airway as part of an adapter directly coupled to the airway of an intubated patient. The adapter is typically proximate the endotracheal tube. As the respiratory gases travel through the patient""s airway and the mainstream gas analyzer adapter, the desired gas, such as CO2 may be monitored. A sidestream gas analyzer diverts a portion of the patient""s inspired and expired respiratory gases from a patient""s airway to be transported to the sidestream gas analyzer for measurement. The analyzed gas sample may be either returned to the patient""s circuit or discarded.
Mainstream gas analyzers are typically utilized on intubated patients, who must be fully sedated. A sidestream side analyzer permits the physician to attach a nasal cannula accessory to the patient, avoiding the need to intubate. Further, a sidestream gas analyzer typically has the ability to measure low flow rates, as may be the case with smaller patients. In other circumstances, a mainstream gas analyzer may be desired, such as when an immediate gas concentration reading is desired, as opposed to the delayed response associated with the sample travel time of sidestream gas analyzers.
In certain conventional patient monitors, a port or interface may be provided to accept input signals from a mainstream CO2 analyzer, but a separate module may be required in an auxiliary rack to permit the monitoring and display of data from a sidestream CO2 analyzer. A separate interface or port may be required on the patient monitor for sidestream CO2 analysis. Accordingly, it would be advantageous to have a patient monitor that is adapted to easily receive and display the signals from a mainstream gas analyzer and a sidestream gas analyzer. It would further be advantageous to have a conversion module adapted to permit the user of a patient monitor to easily convert from a mainstream gas analyzer to a sidestream gas analyzer without requiring additional equipment.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.
One embodiment of the invention relates to a patient monitoring system. The patient monitoring system has a patient monitor with a screen and a mainstream gas input connector configured to receive a mainstream gas concentration signal from a mainstream gas analyzer. The patient monitoring system further includes a sidestream gas analyzer having an output connector, the sidestream gas analyzer configured to transmit a sidestream gas concentration signal via the output connector. The patient monitor receives the sidestream gas concentration signal via the mainstream gas input connector for display on the screen.
The invention is capable of other embodiments and of being practiced or being carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.